(1) Sublimatography
(2) HPLC Method
(3) HPLC-MS（FDA，SGS) and GC-MS(FDA)
Sample Preparation:1. Homogenize the pet foods into the shape of structural pudding.
2. Weigh 2 g of sample into 10mL MeOH/H2O( 60:40)， shake it vigorously.
3. Sonicate 1 min.
4. Mixing the solution by using multi-function mixer whirlpool, let it still 5 min, allow aqueous phase and organic phase separate.
5. Centrifuge it 5 min under 3000 g.
6. Filter the solution with whatman glass fiber filter paper and collect the filtrate.
7. Pipet 0.1 mL of filtrate and dilute with 1.9 MeOH/H2O( 60:40) and 20 mM PBS.
8. Pipet 100 uL for further GC-MS analysis.
Results: Using this sample pre-treatment method assay 8 commercial cat foods ( 15 ppm melamine label claimed, No-FDA recall Porducts), the recovery ratio is from 75%-117%.
http://www.fda.gov/oc/opacom/hottopics/petfood.html
Why the sample pre-treatment matter? the answer is obviously for those chemist whose had nightmare with extraction Melamine from aqueous phase. VIP tips: when obtained a poor recovery result, DO NOT blame the GC-MS, pay attention to the that Melamine solubility in H2O vary under different temperatures.
Note: this method is for products screening only, NOT for any other purpose.
